Attenuation of dark-induced hyperlocomotion by a cholecystokinin antagonist in the nucleus accumbens.

A dark-induced hyperlocomotion paradigm was developed to investigate the role of endogenous cholecystokinin in mediating exploratory locomotor activity in the mesolimbic pathway, where cholecystokinin coexists with dopamine. Microinjection of the cholecystokinin receptor antagonist, proglumide, 10-20 micrograms, into the medial posterior nucleus accumbens, significantly inhibited dark-induced hyperlocomotion, while having no effect on locomotion in the light. These data suggest that endogenous cholecystokinin contributes to behaviorally relevant functions of the activated mesolimbic pathway.